Post-passivation interconnect structure

ABSTRACT

A semiconductor device includes a passivation layer, a first protective layer, an interconnect layer, and a second protective layer successively formed on a semiconductor substrate. The interconnect layer has an exposed portion, on which a barrier layer and a solder bump are formed. At least one of the passivation layer, the first protective layer, the interconnect layer and the second protective layer includes at least one slot formed in a region outside a conductive pad region.

RELATED APPLICATION

The present application is related to co-pending U.S. filing Ser. No. 13/167,946 filed on Jun. 24, 2011, which is expressly incorporated by reference herein in its entirety.

BACKGROUND

Modern integrated circuits are made up of millions of active devices such as transistors and capacitors. These devices are initially isolated from each other, but are later interconnected together to form functional circuits. Typical interconnect structures include lateral interconnections, such as metal lines (wirings), and vertical interconnections, such as via openings and contacts. Interconnections are increasingly determining the limits of performance and the density of modern integrated circuits. On top of the interconnect structures, bond pads are formed and exposed on the surface of the respective chip. Electrical connections are made through bond pads to connect the chip to a package substrate or another die. Bond pads can be used for wire bonding or flip-chip bonding. Flip-chip packaging utilizes bumps to establish electrical contact between a chip's I/O pads and the substrate or lead frame of the package. Structurally, a bump actually contains the bump itself and an “under bump metallurgy” (UBM) located between the bump and an I/O pad.

Wafer level chip scale packaging (WLCSP) is currently widely used for its low cost and relatively simple processes. In a typical WLCSP, post-passivation interconnect (PPI) lines such as redistribution lines (RDLs) are formed on passivation layers, followed by the formation of polymer films and bumps. The PPI formation processes known to the inventors, however, have polymer film peeling issues, which may induce weak interfaces in the PPI structure and cause failures in the device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 are cross-sectional views illustrating various intermediate stages of a method of forming a semiconductor device having a PPI structure in accordance with exemplary embodiments; and

FIG. 6 is a cross-sectional view of a packaging assembly in accordance with exemplary embodiments.

FIGS. 7-9 are cross-sectional views illustrating various intermediate stages of a method of forming a semiconductor device having a PPI structure in accordance with exemplary embodiments;

FIGS. 10-11 are cross-sectional views illustrating a method of forming a PPI structure in accordance with an exemplary embodiment; and

FIGS. 12-13 are cross-sectional views illustrating a method of forming a PPI structure in accordance with exemplary embodiments.

DETAILED DESCRIPTION

The making and using of the embodiments of the disclosure are discussed in detail below. It should be appreciated, however, that the embodiments provide many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the embodiments, and do not limit the scope of the disclosure. Throughout the various views and illustrative embodiments, like reference numerals are used to designate like elements. Reference will now be made in detail to exemplary embodiments illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. In the drawings, the shape and thickness may be exaggerated for clarity and convenience. This description will be directed in particular to elements forming part of, or cooperating more directly with, an apparatus in accordance with the present disclosure. It is to be understood that elements not specifically shown or described may take various forms. Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be appreciated that the following figures are not drawn to scale; rather, these figures are merely intended for illustration.

FIGS. 1-5 illustrate various intermediate stages of a method of forming a PPI structure in a semiconductor device in accordance with an embodiment. Referring first to FIG. 1, a portion of a substrate 10 having electrical circuitry 12 formed thereon is shown in accordance with an embodiment. The substrate 10 may comprise, for example, bulk silicon, doped or undoped, or an active layer of a semiconductor-on-insulator (SOI) substrate. Generally, an SOI substrate comprises a layer of a semiconductor material, such as silicon, formed on an insulator layer. The insulator layer may be, for example, a buried oxide (BOX) layer or a silicon oxide layer. The insulator layer is provided on a substrate, typically a silicon substrate or a glass substrate. Other substrates, such as a multi-layered or gradient substrate may also be used.

Electrical circuitry 12 formed on the substrate 10 may be any type of circuitry suitable for a particular application. In an embodiment, the electrical circuitry 12 includes electrical devices formed on the substrate 10 with one or more dielectric layers overlying the electrical devices. Metal layers may be formed between dielectric layers to route electrical signals between the electrical devices. Electrical devices may also be formed in one or more dielectric layers. For example, the electrical circuitry 12 may include various N-type metal-oxide semiconductor (NMOS) and/or P-type metal-oxide semiconductor (PMOS) devices, such as transistors, capacitors, resistors, diodes, photo-diodes, fuses, and the like, interconnected to perform one or more functions. The functions may include memory structures, processing structures, sensors, amplifiers, power distribution, input/output circuitry, or the like. One of ordinary skill in the art will appreciate that the above examples are provided for illustrative purposes only to further explain applications of some illustrative embodiments and are not meant to limit the disclosure in any manner. Other circuitry may be used as appropriate for a given application.

Also shown in FIG. 1 is an inter-layer dielectric (ILD) layer 14. The ILD layer 14 may be formed, for example, of a low-K dielectric material, such as phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), fluorinated silicate glass (FSG), SiO_(x)C_(y), Spin-On-Glass, Spin-On-Polymers, silicon carbon material, compounds thereof, composites thereof, combinations thereof, or the like, by any suitable method, such as spinning, chemical vapor deposition (CVD), and/or plasma-enhanced CVD (PECVD). It should also be noted that the ILD layer 14 may comprise a plurality of dielectric layers. Contacts (not shown) may be formed through the ILD layer 14 to provide an electrical contact to the electrical circuitry 12. The contacts may be formed of, for example, one or more layers of TaN, Ta, TiN, Ti, CoW, copper, tungsten, aluminum, silver, or the like, or combinations thereof.

One or more inter-metal dielectric (IMD) layers 16 and the associated metallization layers are formed over the ILD layer 14. Generally, the one or more IMD layers 16 and the associated metallization layers (including metal lines 18, via openings 19 and metal layer 20) are used to interconnect the electrical circuitry 12 to each other and to provide an external electrical connection. The IMD layers 16 may be formed of a low-K dielectric material, such as FSG formed by PECVD techniques or high-density plasma CVD (HDPCVD), or the like, and may include intermediate etch stop layers. It should be noted that one or more etch stop layers (not shown) may be positioned between adjacent ones of the dielectric layers, e.g., the ILD layer 14 and the IMD layers 16. Generally, the etch stop layers provide a mechanism to stop an etching process when forming via openings and/or contacts. The etch stop layers are formed of a dielectric material having a different etch selectivity from adjacent layers, e.g., the underlying semiconductor substrate 10, the overlying ILD layer 14, and the overlying IMD layers 16. In an embodiment, etch stop layers may be formed of SiN, SiCN, SiCO, CN, combinations thereof, or the like, deposited by CVD or PECVD techniques.

The metallization layers, including metal lines 18 and via openings 19, may be formed of copper or copper alloys, although they can also be formed of other metals. Further, the metallization layers include a top metal layer 20 formed and patterned in or on the uppermost IMD layer 16T to provide external electrical connections and to protect the underlying layers from various environmental contaminants. The uppermost IMD layer 16T may be formed of a dielectric material, such as silicon nitride, silicon oxide, undoped silicon glass, and the like. In subsequent drawings, semiconductor substrate 10, electrical circuitry 12, ILD layer 14, IMD layers 16, and metallization layers 18 and 19 are not illustrated. The top metal layer 20 is formed as a part of the top metallization layer on the uppermost IMD layer 16T.

Thereafter, a conductive pad 22 is formed in a first region I to contact the top metal layer 20, or alternatively, electrically coupled to top metal layer 20 through a via. The conductive pad 22 may be formed of aluminum, aluminum copper, aluminum alloys, copper, copper alloys, or the like.

With reference to FIG. 1, one or more passivation layers, such as passivation layer 24, are formed over the conductive pads 22 and the uppermost IMD layer 16T. The passivation layer 24 may be formed of a dielectric material, such as undoped silicate glass (USG), silicon nitride, silicon oxide, silicon oxynitride or a non-porous material by any suitable method, such as CVD, PVD, or the like. The passivation layer 24 may be a single layer or a laminated layer. One of ordinary skill in the art will appreciate that a single layer of conductive pad and a passivation layer are shown for illustrative purposes only. As such, other embodiments may include any number of conductive layers and/or passivation layers.

The passivation layer 24 is then patterned by the use of masking methods, lithography technologies, etching processes, or combinations thereof, such that an opening 25 in the first region I and at least one slot 24 a in the second region II are formed. In the first region I, which is the conductive pad region, the passivation layer 24 is patterned to cover the peripheral portion of the conductive pad 22, and to expose the central portion of conductive pad 22 through the opening 25. In a second region II that is adjacent to the conductive pad region, the passivation layer 24 is patterned to provide the slot 24 a for improving the adhesion at an interface between the passivation layer 24 and the subsequent deposited material layers. In some embodiments, more than two slots 24 a are formed in the passivation layer 24. It should also be noted that the placement of the slots 24 a is provided for illustrative purposes only and that the specific locations and patterns of the slots 24 a may vary and may include, for example, an array of slots, lines of slots, staggered slots, a mesh-shape slot or the like. The illustrated slot sizes are provided for reference only and are not intended to be actual sizes or actual relative sizes.

Next, as shown in FIG. 2, a first protective layer 26 is formed on the passivation layer 24, filling the opening 25 and the slots 24 a. The first protective layer 26 is the patterned to form an opening 27, through which at least a portion of the conductive pad 22 is exposed again. The first protective layer 26 filling the slot 24 a forms a foot portion 26 a embedded in the passivation layer 24. The first protective layer 26 may be, for example, a polymer layer. The polymer layer may be formed of a polymer material such as an epoxy, polyimide, benzocyclobutene (BCB), polybenzoxazole (PBO), and the like, although other relatively soft, often organic, dielectric materials can also be used. The formation methods include spin coating or other methods.

Thereafter, a PPI structure 28 is formed and patterned on the first protective layer 26 and electrically connected the conductive pad 22 through the opening 27 as shown in FIG. 3. The PPI structure 28 that is an interconnect layer includes an interconnect line region 28I and a landing pad region 28P. The interconnect line region 28I and the landing pad region 28P may be formed simultaneously, and may be formed of a same conductive material. In an embodiment, the interconnect line region 28I extends to electrically connect the conductive pad 22 through the opening 27, and a bump feature will be formed over and electrically connected to the landing pad region 28P in subsequent processes. The PPI structure 28 may include, but is not limited to, for example copper, aluminum, copper alloy, or other mobile conductive materials using plating, electroless plating, sputtering, chemical vapor deposition methods, and the like. In some embodiments, the PPI structure 28 may further include a nickel-containing layer (not shown) on top of a copper-containing layer. In some embodiments, the PPI structure 28 may also function as power lines, re-distribution lines (RDL), inductors, capacitors or any passive components. Through the routing of PPI structure 28, the landing pad region 28P may be, or may not be, directly over the conductive pad 22.

With reference to FIG. 3, a second protective layer 30 is then formed on the substrate 10 to cover the PPI structure 28 and the exposed portions of the first protective layer 26. Using photolithography and/or etching processes, the second protective layer 30 is further patterned to form an opening 32 exposing at least a portion of the landing pad region 28P. The formation methods of the opening 32 may include lithography, wet or dry etching, laser drill, and/or the like. In some embodiments, the second protective layer 30 is formed of a polymer layer, such as an epoxy, polyimide, benzocyclobutene (BCB), polybenzoxazole (PBO), and the like, although other relatively soft, often organic, dielectric materials may also be used. In some embodiments, the second protective layer 30 is formed of a non-organic material selected from undoped silicate glass (USG), silicon nitride, silicon oxynitride, silicon oxide, and combinations thereof.

In order to protect the exposed portion of the landing pad region 28P, the process proceeds to the formation of a barrier layer 34 within the opening 32 as shown in FIG. 4. The barrier layer 34 is formed on the landing pad region 28P within the opening 32 to prevent copper in the PPI structure 28 from diffusing into bonding material, such as solder alloy, that is used to bond the substrate 10 to external features. The prevention of copper diffusion increases the reliability and bonding strength of the package. The barrier layer 34 may include nickel (Ni), tin, tin-lead (SnPb), gold (Au), silver, palladium (Pd), indium (In), nickel-palladium-gold (NiPdAu), nickel-gold (NiAu), a Ni-based alloy, an Au-based alloy, or a Pd-based alloy, other similar materials, or an alloy by an electroless plating process or an immersion plating process. The barrier layer 34 has a thickness about 0.1-10 μm. In one embodiment, the barrier layer 34 is a triple-layer structure including an electroless Ni layer, an electroless Pd layer, and an immersion Au layer, which is also known as an ENEPIG structure. For example, the ENEPIG structure may have the electroless Ni layer with a thickness of at least 2 μm, the electroless Pd layer with a thickness of at least 0.02 μm and the immersion Au layer with a thickness of at least 0.01 μm. In one embodiment, the barrier layer 34 is a dual-layer structure including an electroless Ni layer and an electroless Pd layer, named an ENEP structure. In one embodiment, the barrier layer 34 is a single-layer structure including an electroless Ni layer, which is also known as an EN structure. In one embodiment, the barrier layer 34 is a dual-layer structure including an electroless Ni layer and an immersion Au layer, which is also known as an ENIG structure.

As shown in FIG. 5, a solder bump 36 is formed on the barrier layer 34. In one embodiment, the solder bump 36 is formed by attaching a solder ball on the barrier layer 34 and then reflowing the material. The solder bump 36 may include a lead-free pre-solder layer, SnAg, or a solder material including alloys of tin, lead, silver, copper, nickel, bismuth, or combinations thereof. A bump structure is therefore completed on a semiconductor device. The presented embodiments provide the slots 24 a in the passivation layer 24 to enhance the interface adhesion between the passivation layer 24 and the first protective layer 26. This can improve the strength in the PPI structure, and the peeling and cracking of the polymer layer may be reduced and/or eliminated. Accordingly, in packaging assembly processes, joint reliability can be increased and bump fatigue can be reduced.

After the bump formation, for example, an encapsulant may be formed, a singulation process may be performed to singulate individual dies, and wafer-level or die-level stacking or the like may be performed. It should be noted, however, that embodiments may be used in many different situations. For example, embodiments may be used in a die-to-die bonding configuration, a die-to-wafer bonding configuration, a wafer-to-wafer bonding configuration, die-level packaging, wafer-level packaging, or the like.

FIG. 6 is a cross-sectional diagram depicting an exemplary embodiment of a flip-chip assembly. The structure shown in FIG. 5 is flipped upside down and attached to another substrate 100 at the bottom of FIG. 6. The substrate 100 may be a package substrate, board (e.g., a printed circuit board (PCB)), a wafer, a die, an interposer substrate, or other suitable substrate. The bump structure is coupled to the substrate 100 through various conductive attachment points. For example, a conductive region 102 is formed and patterned on the substrate 100. The conductive region 102 is a contact pad or a portion of a conductive trace, which is presented by a mask layer 104. In one embodiment, the mask layer 104 is a solder resist layer formed and patterned on the substrate 100 to expose the conductive region 102. The mask layer 104 has a mask opening, which provides a window for solder joint formation. For example, a solder layer including alloys of tin, lead, silver, copper, nickel, bismuth, or combinations thereof may be provided on the conductive region 102. The substrate 10 can be coupled to the substrate 100 to form a joint solder structure 106 between the barrier layer 34 and the conductive region 102. An exemplary coupling process includes a flux application, chip placement, reflowing of melting solder joints, and/or cleaning of flux residue. The integrated circuit substrate 10, the joint solder structure 106, and the other substrate 100 may be referred to as a packaging assembly 200, or in the present embodiment, a flip-chip packaging assembly.

FIGS. 7-9 illustrate various intermediate stages of an exemplary method of forming a PPI structure in a semiconductor device in accordance with an alternative embodiment. Unless specified otherwise, the reference numerals in these embodiments represent like elements in the embodiments illustrated in FIGS. 1-6.

Referring to FIG. 7, the first protective layer 26 is formed on the passivation layer 24 to fill the opening 25. The first protective layer 26 is the patterned to form the opening 27 within the first region I, through which at least a portion of the conductive pad 22 is exposed again. The first protective layer 26 is also patterned to form another slot 26 b in the second region II, which exposes at least one portion of the passivation layer 24 outside the conductive pad region. In some embodiments, more than two slots 26 b are formed in the first protective layer 26. It should also be noted that the placement of the slots 26 b is provided for illustrative purposes only and that the specific locations and patterns of the slots 26 b may vary and may include, for example, an array of openings, lines of slots, staggered slots, a mesh-shape slot or the like. The illustrated slot sizes are provided for reference only and are not intended to be actual sizes or actual relative sizes.

Thereafter, as shown in FIG. 8, the PPI structure 28 is formed on the first protective layer 26 to fill the openings 27 and 26 b. The PPI structure 28 is then patterned to provide the interconnect line region 28I, the landing pad region 28P, and a dummy region 28D. In an embodiment, the dummy region 28D is formed in at least one of the slots 26 b in the first protective layer 26, and electrically separated from the landing pad region 28P and the interconnect line region 28I. In some embodiments, the dummy region 28D includes the PPI material filling more than two slots 26 b and continuously extending to the surface of the first protective layer 26.

With reference to FIG. 8, the second protective layer 30 is then formed on the substrate 10 to cover the PPI structure 28 and the exposed portions of the first protective layer 26. Next, the second protective layer 30 is patterned to form the opening 32 exposing the landing pad region 28P. As shown in FIG. 9, the barrier layer 34 and the solder bump 36 are formed on the exposed portion of the landing pad region 28P.

The presented embodiments provide the slots 26 b in the first protective layer 26 to enhance the interface adhesion between the PPI structure 28 and the first protective layer 26. This can improve the strength in the PPI structure, and the peeling and cracking of the polymer layer may be reduced and/or eliminated. Accordingly, in packaging assembly processes, joint reliability can be increased and bump fatigue can be reduced.

FIGS. 10-11 illustrate a method of forming a PPI structure in a semiconductor device in accordance with an alternative embodiment. Unless specified otherwise, the reference numerals in these embodiments represent like elements in the embodiments illustrated in FIGS. 1-9.

As shown in FIG. 10, the PPI structure 28 is formed on the first protective layer 26 to fill the opening 27. The PPI structure 28 is then patterned to provide the interconnect line region 28I, the landing pad region 28P, and the dummy region 28D. The dummy region 28D is electrically separated from the landing pad region 28P and the interconnect line region 28I. In an embodiment, the dummy region 28D includes at least one slot 28 a, exposing at least one portion of the underlying first protective layer 26. In some embodiments, more than two slots 28 a are formed in the dummy region 28D. It should also be noted that the placement of the slots 28 a is provided for illustrative purposes only and that the specific locations and patterns of the slots 28 a may vary and may include, for example, an array of slots, lines of slots, staggered slots, a mesh-shape slot or the like. The illustrated slot sizes are provided for reference only and are not intended to be actual sizes or actual relative sizes.

With reference to FIG. 11, the second protective layer 30 is then formed on the substrate 10 to cover the PPI structure 28 and the exposed portions of the first protective layer 26. The second protective layer 30 also fills the slots 28 a of the PPI structure 28 so as to form foot portions 30 a embedded in the dummy region 28D. The second protective layer 30 is further patterned to form the opening exposing the landing pad region 28P for the formation of the barrier layer 34 and the solder bump 36. The presented embodiments provide the slots 28 a in the PPI structure 28 to enhance the interface adhesion between the first protective layer 26 and the second protective layer 30. This can improve the strength in the PPI structure, and the peeling and cracking of the polymer layer may be reduced and/or eliminated. Accordingly, in packaging assembly processes, joint reliability can be increased and bump fatigue can be reduced.

FIGS. 12-13 illustrate a method of forming a PPI structure in a semiconductor device in accordance with an alternative embodiment. Unless specified otherwise, the reference numerals in these embodiments represent like elements in the embodiments illustrated in FIGS. 10-11.

As shown in FIG. 12, after the formation of the PPI structure 28 with the dummy pad region 28D shown in FIG. 10, the second protective layer 30 is formed to cover the PPI structure 28 and the exposed portions of the first protective layer 26. The second protective layer 30 also fills the slots 28 a so as to form foot portions 30 a embedded in the dummy region 28D. The second protective layer 30 is also patterned to form the opening 32 exposing the landing pad region 28P of the PPI structure 28 for the formation of the barrier layer 34 and the solder bump 36. In addition, the second protective layer 30 is patterned to form at least one slot 30 b exposing at least one portion of the underlying dummy region 28D. In some embodiments, the second protective layer 30 includes more than two slots 30 b. It should also be noted that the placement of the slots 30 b is provided for illustrative purposes only and that the specific locations and patterns of the slots 30 b may vary and may include, for example, an array of slots, lines of slots, staggered slots, a mesh-shape slot or the like. The illustrated slot sizes are provided for reference only and are not intended to be actual sizes or actual relative sizes.

With reference to FIG. 13, the process proceeds to the formation of the barrier layer 34 within the opening 32 on which the solder bump 36 is formed. The barrier layer 34 is also formed in the slots 30 b of the second protective layer 30, serving as dummy metal plugs 34 a physically and electrically connecting the dummy region 28D of the PPI structure 28. The presented embodiments provide the slots 30 b in the second protective layer 30 to enhance the interface adhesion between the PPI structure 28 and the second protective layer 30. This can improve the strength in the PPI structure, and the peeling and cracking of the polymer layer may be reduced and/or eliminated. Accordingly, in packaging assembly processes, joint reliability can be increased and bump fatigue can be reduced.

In according with one aspect of exemplary embodiments, a semiconductor device includes a semiconductor substrate, a passivation layer overlying the semiconductor substrate, and an interconnect layer overlying the passivation layer. The interconnect layer includes a line region and a landing pad region. A protective layer overlies the interconnect layer and exposes the landing pad region of the interconnect layer. A barrier layer is formed on the exposed portion of the pad region, and a solder bump formed on the barrier layer. The barrier layer is formed of at least one of a nickel (Ni) layer, a palladium (Pd) layer and a gold (Au) layer.

In accordance with another aspect of exemplary embodiments, a packaging assembly includes a semiconductor device connected by a joint to a substrate. The semiconductor device includes a post-passivation interconnect (PPI) layer having a line region and a landing pad region, a polymer layer covering the line region of the PPI layer and exposing the landing pad region of the PPI layer, and a barrier layer on the exposed landing pad region of the PPI layer. The substrate includes a conductive region. A joint solder structure is formed between the barrier layer of the semiconductor device and the conductive region of the substrate. The barrier layer is formed of at least one of a nickel (Ni) layer, a palladium (Pd) layer and a gold (Au) layer.

In accordance with another aspect of to exemplary embodiments, a method of forming a semiconductor device includes the following steps: forming a passivation layer overlying a semiconductor substrate; forming an interconnect layer overlying the passivation layer, forming a protective layer overlying the interconnect layer; forming an opening in the protective layer to expose a landing pad region of the interconnect layer; forming a barrier layer on the pad region within the opening of the protective layer by an electroless plating process or an immersion plating process; and forming a solder bump on the barrier layer. The barrier layer is formed of at least one of a nickel (Ni) layer, a palladium (Pd) layer and a gold (Au) layer.

In the preceding detailed description, the disclosure is described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications, structures, processes, and changes may be made thereto without departing from the broader spirit and scope of the disclosure. The specification and drawings are, accordingly, to be regarded as illustrative and not restrictive. It is understood that the disclosure is capable of using various other combinations and environments and is capable of changes or modifications within the scope of inventive concepts as expressed herein. 

What is claimed is:
 1. A semiconductor device, comprising: a semiconductor substrate having a first region and a second region, wherein the first region is a conductive pad region, and the second region is adjacent to the first region; a passivation layer overlying the semiconductor substrate; a first protective layer overlying the passivation layer; an interconnect layer overlying the first protective layer; a second protective layer overlying the interconnect layer and comprising an opening exposing a portion of the interconnect layer; a barrier layer formed on the exposed portion of the interconnect layer; and a solder bump formed on the barrier layer, wherein each of the first protective layer and the interconnect layer comprise a plurality of slots formed in the second region, and the second protective layer fills each slot of the plurality of slots in the interconnect layer.
 2. The semiconductor device of claim 1, wherein the barrier layer comprises at least one of a nickel (Ni) layer, a palladium (Pd) layer, or a gold (Au) layer.
 3. The semiconductor device of claim 1, wherein the interconnect layer comprises copper.
 4. The semiconductor device of claim 1, further comprising a conductive pad formed on the semiconductor substrate in the first region, wherein the conductive pad is partially covered by the passivation layer and the first protective layer, and the conductive pad is electrically connected to the interconnect layer.
 5. The semiconductor device of claim 1, wherein the interconnect layer fills the plurality of slots of the first protective layer.
 6. The semiconductor device of claim 5, wherein the interconnect layer comprises a landing pad region exposed by the opening of the second protective layer, and a dummy region formed in the slots of the first protective layer and electrically separated from the landing pad region.
 7. The semiconductor device of claim 1, wherein the first protective layer comprises a polymer.
 8. The semiconductor device of claim 1, wherein the interconnect layer comprises a landing pad region exposed by the second protective layer and a dummy pad region electrically separated from the landing pad region, and the dummy pad region comprising the plurality of slots in the second region.
 9. The semiconductor device of claim 1, wherein the second protective layer comprises a plurality of slots exposing the dummy pad region of the interconnect layer.
 10. The semiconductor device of claim 9, wherein the barrier layer fills the plurality of slots in the second protective layer.
 11. The semiconductor device of claim 1, wherein the second protective layer comprises a polymer.
 12. A packaging assembly, comprising: a semiconductor device having a first region and a second region adjacent to the first region, and comprising: a conductive pad formed on the first region; a passivation layer formed on the first region and the second region, wherein the passivation layer comprises a first opening in the first region to partially cover the conductive pad; a first polymer layer overlying the passivation layer and comprising a second opening in the first region to partially cover the first opening and partially expose the conductive pad; a post-passivation interconnect (PPI) structure overlying the first polymer layer and filling the second opening of the first polymer layer, the PPI structure having a dummy pad region in the second region; a second polymer layer overlying the PPI structure and comprising a third opening exposing a landing pad region of the PPI structure, the landing pad region electrically separated from the dummy pad region, and the second polymer layer further comprising a fourth opening exposing a portion of the dummy pad region; and a barrier layer on the exposed landing pad region of the PPI structure and on the exposed portion of the dummy pad region, wherein the barrier layer comprises at least one of a nickel (Ni) layer, a palladium (Pd) layer or a gold (Au) layer; a substrate comprising a conductive region, the substrate separate from the semiconductor device; and a joint solder structure between the barrier layer of the semiconductor device and the conductive region of the substrate.
 13. The packaging assembly of claim 12, wherein the first polymer layer comprises a plurality of slots in the second region, and the dummy pad region of the PPI structure fills the plurality of slots of the first polymer layer.
 14. The packaging assembly of claim 12, wherein the dummy pad region comprises a plurality of slots in the second region.
 15. The packaging assembly of claim 14, wherein the second polymer layer fills the plurality of slots in the dummy pad region of the PPI structure.
 16. A semiconductor device, comprising: a semiconductor substrate having a first region and a second region, wherein the first region is a conductive pad region, and the second region is adjacent to the first region; a passivation layer overlying the semiconductor substrate; a first protective layer overlying the passivation layer; an interconnect layer overlying the first protective layer, the interconnect layer having a landing pad region and a dummy pad region electrically separated from the landing pad region; a second protective layer overlying the interconnect layer and comprising a first opening exposing the landing pad region and a second opening exposing a portion of the dummy pad region; a barrier layer formed on the landing pad region and the exposed portion of the dummy pad region; and a solder bump formed on the barrier layer formed on the landing pad region.
 17. The semiconductor device of claim 16, wherein the first protective layer comprises a plurality of slots in the second regions, and the dummy pad region fills the plurality of slots and contacts a top surface of the passivation layer.
 18. The semiconductor device of claim 16, wherein the dummy pad region comprises a plurality of dummy pads electrically separated from one another, and the second protective layer fills a space between adjacent dummy pads of the plurality of dummy pads.
 19. The semiconductor device of claim 16, wherein the landing pad region is in the second region.
 20. The semiconductor device of claim 16, wherein the barrier layer formed on the dummy pad region has a top surface above a top surface of the second protective layer. 